1. Field of the Invention
The present invention relates an an integrated optical disc pickup which is a key component of optical disc devices for recording or reproducing information.
2. Description of the Prior Art
Generally, integrated optical disc pickups comprise a system of a multiplicity of lenses, a beam splitter and photodetectors in combination.
However, the conventional optical pickup is cumbersome to assemble and adjust and is therefore costly, while the optical pickup, which is large-sized, has the drawback of requiring a prolonged access time.
To overcome the drawbacks, Nishihara et al. have proposed an integrated optical disc pickup (see IEICE (The Institute of Electronics, Information and Communication Engineers) Technical Report, OQE85-72 (1985), Vol. 85, No. 136, pp. 39-46. The proposed pickup includes a focusing grating coupler for focusing a laser beam on the optical disc and requires control of the absolute wavelength of the light source since the focusing characteristics of the coupler is dependent on the wavelength of the light source. Insofar as a semiconductor laser is used as the light source, accordingly, the proposed arrangement involves extreme difficulties and is infeasible.